Each nephron consists of functionally distinct segments of tubule cells. While the functional characteristics of each nephron segments being well defined, the metabolic characteristics have been poorly defined. In this project, studies will be carried out first to examine and characterize the cell metabolism in an isolated, defined segment of single nephron, and then to evaluate the ionic and hormonal regulation of the cell metabolism. More specifically, the following experiments will be done in each defined nephron segment, i.e., proximal convolution, pars recta, thick ascending loop of Henle, distal convolution, and cortical collecting tubules. 1. Define the basic metabolic characteristics; glucose oxidation, gluconeogenesis, other substrates' oxidation, etc. 2. Examine the effects of changes in H ion, Ca ions, and phosphate in the extracellular milieu on the cell metabolism. 3. Examine changes in cell cyclic AMP in response to parathyroid hormone and calcitonin, and the modulating effects of changes in the ionic composition of extracellular milieu as described in #2 on cell cyclic AMP. 4. Determine the effects of parathyroid hormone, calcitonin, and cyclic AMP on the cell metabolism in each hormone-sensitive segment of nephron. 5. Determine the effects of cholera toxin, and calcium regulating pharmacological agents (i.e., calcium-ionophores, verapamile, etc.) on the cell metabolism. These studies will provide further information on the characteristics of renal cell metabolism in each defined nephron segment, and its control by ions and hormones. The studies may also help understand the mechanisms of of action of parathyroid hormone and calcitonin, and the relative roles of cyclic AMP and calcium ion as possible intracellular mediators of the hormone action.